A Systems Approach to Disease Resistance Against Necrotrophic Fungal Pathogens

Abstract

The overall objective of this project is to identify sources of disease resistance in lettuce against Botrytis cinerea and Sclerotinia sclerotiorum, two economically important fungal pathogens. Furthermore we will demonstrate how systems biology approaches can be exploited to facilitate breeding of quantitative resistance to ubiquitous pathogens in horticultural crops. Network analysis, along with quantitative genetic studies, will identify novel alleles (and associated markers) for increasing the resistance of lettuce to both B. cinerea and S. sclerotiorum.

Description

Pests and Pathogens. The proposal will identify alleles that can be used to increase disease resistance in lettuce against two economically important pathogens (B. cinerea and S. sclerotinia) and demonstrate a novel approach for breeding resistance to plant pathogens. B. cinerea and S. sclerotiorum have a similar necrotrophic lifestyle, a similar repertoire of genes involved in pathogenesis and a broad host range causing disease on many horticultural crops. Hence strategies to improve disease resistance against these pathogens will have wide application.

Systems approaches incorporating mathematical and computational modelling. Our novel approach (successfully deployed in the model plant Arabidopsis) uses mathematical network inference from transcriptome data to identify key regulatory genes in the plant defence response. This network analysis will also enhance the identification of candidate genes underlying resistance QTL from traditional genetic approaches.

Broad relevance, tackling a problem spanning a range of horticultural crops. We will investigate whether key defence regulatory genes are conserved across horticultural crops and hence applicable to multiple breeding programs. Crucially we will demonstrate the feasibility of a systems network approach to understanding and improving quantitative disease resistance in non-model organisms. This approach relies on a single data set and hence could be easily applied to other crops and patho-systems.

Relevance to Industry

B. cinerea and S. sclerotiorum cause substantial losses on field-grown and protected lettuce crops, an industry worth almost £200M/yr in the UK. B. cinerea is a particular problem post-harvest, whereas S. sclerotiorum can result in up to 50% crop loss pre-harvest. Chemical control is problematic with restrictions on spraying and fungicides being medium-high risk for development of resistance. Development of host resistance is a more sustainable solution, but has been an intransigent problem for breeders. This proposal demonstrates a novel approach to breeding for quantitative disease resistance against these pathogens using systems biology. The development of resistant lettuce varieties will have considerable economic benefits. A 50% reduction in disease would save £10M/yr given an average crop loss of 10%. In addition, 90% of lettuce crops are treated with fungicides with 2-3 sprays per crop targeted at Botrytis and Sclerotinia (equivalent to ~22 000 ha). A 50% reduction in these applications due to deployment of more resistant lettuce varieties would save >£7M/yr given application costs of £150/ha. Reduced crop losses and more efficient resource use would also be of environmental benefit.

Successful demonstration of network analysis for identifying disease resistance alleles and/or conservation of key defence genes across species will provide genes and/or methodology for use in other horticultural crops (such as tomato and Brassica) and dramatically extend the impact and strategic relevance of this proposal.